Advances made in animal handling and in the acquisition, reconstruction and storage of magnetic resonance (MR) data will make possible experiments that are technically and experimentally complex. For example, initial MR images that were made 12 to 18 months ago of the liver of rats consisted of 1 image with a pixel size of 500 by 500 mum and a slice thickness of 5.0mm. Because of the relatively long imaging time (30-60 mm), respiratory motion that was transferred through the diaphragm to the liver resulted in blurring of the image with some loss of resolution. Because of these inherent limitations, structures or lesions in the liver less than approximately 2 mm in diameter would probaby not be detected. Recent developments, however, that will allow the production of multiple, contiguous images as thin as 1.25 mm and with a pixel size of 200 x 200 mum are as follows: 1. The synchronization of respiratory movements and signal detection. This will effectively eliminate motion artifacts produced by breathing. 2. The adaptation and installation of a 3-dimensional Fourier Transformation program for the imaging devise. This allows the selective excitation of a volume of tissue with the subsequent production of multiple, contiguous images from that region. 3. The changes in imaging devise from the 1.00 meter, 1.5 Tesla research system to the 0.30 meter, 2.0 Tesla CSI system. This system (CSI) was designed for the imaging of small animals.